Optical spectroscopy is a known method of measuring the optical properties of a material such as gas, liquid, solid, chemical compound, biological material such as biological fluids or tissue, paint or coating or other material.
A common form of spectroscopy measures the spectral properties of the desired material by illuminating the material with light and then measuring the light remitted or emitted by a material. The relative response of the material to light of different energy levels is useful characteristic of a material, sometimes called the optical signature that can be used to identify the nature of a material or determine how much of a material is present.
When there is a mixture of materials the optical signature of the mixture is typically some combination of the optical signatures of the components of the mixture. Analysis of the relative amounts of wavelengths characteristic of a particular material either by visual inspection, or more commonly by computer based algorithms, can be used to determine how much of a material is present in the mixture.
The optical signatures or spectra of a material are typically represented as an intensity of emission or absorbance at a particular wavelength or wavelength range and are often presented as a two dimensional graph with wavelength on one axis and intensity or absorbance as a function of wavelength on the other axis. These graphs can be simple or complex in shape and the range between intensities or absorbance can be very great for different wavelengths.
The measurement tools used to measure the intensity of absorbance or emission of light from a compound are usually referred to as spectrographs or spectrometers and are well known. One limitation of these devices is the difficulty of making accurate measurements over wide ranges of intensity values.
Considering the case of reflectance spectroscopy, for some samples the light emitted from a sample may be very bright at some wavelengths of interest and very faint at others. Often the detector measurement range is exceeded.
Detectors also often have their own wavelength response due to the spectral properties of the detection system, which can further limit the capability to make an accurate measurement.
Most spectrometers are designed to work with a light source suitable for illuminating the material to be measured to provide wavelengths useful for measurement of the desired optical properties of the material. The measurement device is typically calibrated against the optical properties of the light source. This can also become a limiting factor in the ability of the system to make measurements since some light sources do not provide enough of the wavelengths useful for the measurement.
Often a spectrograph or spectrometer system has to be set up for a particular application or a material to be measured and is difficult to reconfigure quickly for the measurement of a wide range of compounds.
Thus there has gone unmet a need for spectral measurement systems and spectroscopy light sources that provide improved dynamic range and improved accuracy, and can be configured quickly to measure accurately a wide range of samples.